Upgrading manganese ores using hf and hsif as leaching materials



United States Patent Oliice 3,330,649 UPGRADING MANGANESE DRES USING HF AND H2SiF6 AS LEACHING MATERIALS Jay Y. Welsh, Catonsville, Md., assigner to Manganese Chemicals Corporation, Baltimore, Md., a corporation of Minnesota Filed May 27, 1964, Ser. No. 370,569 6 Claims. (Cl. 75-101) This invention relates to the art of hydr-ometall'urgically beneciating manganese ores whose manganese con-tent is largely in the form of manganese dioxide, and is concerned with the upgrading of ores which are relatively high in MnOz but which contain significant amounts of silica and other impurities. The invention is particularly concerned with the provision of a cyclical process of upgrading such ores with simultaneous production of certain by-products having substantial economic value. The invention has both process and product aspects.

`By the expression manganese ores relatively high in MnO2 are here meant ores whose content of Mn02 amount to at least 50% by weight of the total.

Manganese ores Ialmost invariably contain at least some Mut2 and Mn+3. Also, they contain silica in greater or lesser amount together with measurable amounts of alumina and of at least one compound of at least one mem ber (or, usually, of a plurality of members) of the metals group consisting of Fe, Prb, Zn and Cu and sometimes an oxidic compound of an alkali or/and alkaline earth metal. In the specific examples appearing hereinbelow there are set out partial analyses (limited to manganese and those impurities occurring in more substantial amounts) of several representative manganese ores relatively high in MnOz. In this connection, it should be noted that (l) some of the frequently encountered impurities in manganese ores are present amongst the gangue components of the ore, while `(2) some of them are built into the manganese dioxide crystal. Generally speaking, alkali oxides and up to about 5.0% Fe and up to about 0.7% P-b and smaller amounts of Cu, Zn, P and As yare (or appear to be) incorporated in the MnO2 structure. As will be :brought out hereinbelow, impurities of the 1 type above are amenable to the upgrading process of the present invention, whereas some of the impurities of the 2 type are relatively very poorly removable by the process.

In its broader aspect, the upgrading process of the present invention comprises treating an ore, of the composition above described, in particulate form, with an aqueous solution of la dissolving agent of the group consisting of HF, HZSiFs andmixtures of HF and HZSFS whereby to extract or leach out non-Mn02 components of the ore which yare soluble in such solution (pure MnOz is not soluble in such solution), `and separating the Iresulting liquid phase (containing fluorine values in the Iform of silicofluorides and hydrouoric acid, and solubilized impurities leached from the ore), and the resulting Solid phase, i.e., the upgraded ore, by conventional separatory measures e.g., decantation, tilt-ration, `and the like. The aforesaid treating step may be carried out in a leach columncontaining more or less coarse MnO2 ore particles (e.g., particles from one-fourth inch diameter to particles as small as 6 mesh or smaller); or, the par- Patented July 1l, 1967 ticulate ore may be slurried With the above-described liquid treating agent, in which latter event the maximum particle size is Adetermined by its slurrying ability.

Since Si02 and A1203 almost always are encountered in the ore, the treating agent includes lboth hydrouosilicic acid and hydrouoric acid, -since the latter is needed for decomposing the SiO2 `and to assist in the lbreak-down of the A1203. The reaction of HF with SiO2 produces SiF4 which becomes solubilized as HZSiF. The aforesaid separated aqueous phase contains, then, the so-formed H2SiF6 and the solubilized metals: apparently, lany solubilized iron, lead, zinc, copper and Mnt2 and Mui'3 values are present as silicouorides, and the aluminum probably as complex silicouorides.

In connection with the above-described process, it is to be noticed that all of the solubilized metal silicofluorides can, if so desired, be recovered; also, that uorine values can be regenerated. Whatever HF Ibecomes used up in decomposing SiO2 represents the extent to which HZSiFs builds up in said liquid phase, `anti hence part of the H2SiF6 content can be separated from the liquid phase as a by-pr-oduct having econo-mic value.

As will, then, be appreciated, the principles of the present invention quite naturally ud economic expression in a cyclic process in which (a) raw ore and make-up HF are continuously or intermittently added to the closed circuit, land (b) upgraded `ore and by-product H2SiF6 are continuously or intermittently removed from the circuit. The hereinabove-described general process is integrated into the cyclic process, which latter may be described as follows:

Particulate IMnOg ore (of the gangue-containing kinds described hereinbefore) and an aqueous solution of H2SiF6 and HF are continuously introduced into a dissolving zone to leach out the ore, more or less completely, gangue constitutents of such ore thereby yielding a solid phase consisting essentially of upgraded MnO2 ore and a liquid (aqueous) phase containing metal 'silicouorides (derived from impurities in the raw ore), the introduced H2SiF6 and additional HZSiFG (derived from the SiO2 decomposed out of the raw ore). The solid and liquid phases are contin-uou-sly separated from each other, and the solid phase may be and preferably is washed t-o a reasonable extent, and is withdrawn from the circuit as product (upgraded) MnO2 ore. A part of the liquid phase is recycled to the dissolving zone, While the remainder of the separated liquid phase is continuously treated with a uosilicatedecomposing agent so as to regenerate, from the soluble silic-ouorides contents of the liquid phase, H2-SiF6 in the -form of an aqueous solution suitable for recycling to the dissolving zone. The additional HZSiFs which had been derived -from the SiO2 content of the raw ore may be, and preferably is, Withdrawn from the circuit as =by product H2SiF6. The by-.product H2SiF6 desirably should equal in amount the make-up HF plus the silica leached lfrom the raw ore. Preferably, the silicouoride and fluoride-decomposing agent is sulphuric acid (e.g., H2SO4 of about concentration), and in this decomposing step the metal silicoiluorides (of the liquid phase) preferably lare converted to metal sulphates. To the extent that Mn+2 and/or Mnt3 values (present in the raw ore) had been solubilized and carried in the aforesaid ,liquid phase, this manganese will-through the reaction with H2SO4--be converted to manganese sulphate, `and the latter may be recovered and put to use either as such or as starting material for preparing manganese metal or some other manganese compound. For recovering these manganese values I may treat the still bottoms sludge with MnO and H20 and adjust the pH to 5.0-5.5, at which point Fe and Al values precipitate leaving an `aqueous phase consisting largely or wholly of a solution of MnSO4. While such recovery of Mn values from 'che still bottoms sludge is not a necessary step in my cyclic process, it has such economic or technological worth as to be included in yany actual processing plant flow sheet, such for illustrative purposes as the sole figure of the appended drawing.

The liquid-vapor equilibria within the distilling column impose the most basic theoretical limit on composition. These data dictate that the free HF in the recycle liquor should not exceed (and preferably not more than 3%) if HF losses are to be avoided in the water balance, and that the HzSiFG concentration in the recycle liquor cannot exceed 41 to 43% (depending on the HF concentration). Values ought not to be exceeded, since a water balance by means of a distilling column otherwise would be impossible.

The method of maintaining water balance is of basic importance in defining the process. Otherwise most of the iiuoride values would have to be discarded, with poor economics, or complicated and expensive reclaiming processes would have to be employed. With the process as defined, operated in an optimum manner, water balance is maintained by volatilization, i.e., all of the excess wash water (over that required for the 30% HZSiFG byproduct) is removed from the top of the distillation column. All metals leached are removed as sludge sulfates with a minimum of concentrated (70%) H2504.

The beneficiation effected on most commercial, large volume, Mn ores is outstanding. A common metallurgical grade ore can easily be upgraded to far surpass the best chemical grade ores.

In my complete cyclic process, that which cycles is the majority of the dissolving agent (H2SiF6 and HF, in aqueous solution) which is present in excess. The particulate ore passes into and out of the closed circuit, as does the wash water. The HF which is (continuously or intermittently) added as make-up HF departs from the circuit in the H2SiF6 by-product. The added H2804 departs as sulphates and waste free acid in the still bottoms sludge. In the still itself there is eliminated the Water which entered the circuit as wash Water, less that amount of water which goes out in the 30% solution of HZSiF by-product and less the small amounts which depart the circuit in the Mn02 product filter cake and in the still bot toms sludge.

The process of the present invention will now be described in greater particularity and with reference to the accompanying drawing, in which The single gure is a flow sheet of the complete process.

In the drawing, 1 represents a reaction vessel provided with an agitator means 2. Raw ore is fed to the reaction vessel as at 3, While a solution of H2SiF6 is delivered to the vessel through pipe 4 and make-up HF is delivered as at 5. A heat-exchange means 6 is installed in reaction vessel 1 to maintain the temperature of the reaction mixture at, say, about 90 C.

Reaction mixture slurry is transferred from vessel 1, by means of pump 8 and conduit 10, to a thickener 11 of known type, wherein the solids content of the slurry is countercurrently washed with water admitted through pipe 12. Eiuent from the thickener is transferred, through pipe to places of use (to be described hereinbelow), whilst the partially thickened solids are pumped, by pump 13 to the next in series of a series of generally similar thickeners, e.g. six, more or less, wherein the solids are washed free from hydrouoric acid, hydrouosilicic acid, and salts of hydrofluosilicic acid, and the wash waters 'are combined, for Ithe recovery of values. After the washing has been carried out to an acceptable pure solids product, the resulting partially dewatered slurry of particulate MnOZ is delivered through conduit 1S to a filter 16. The resulting filter cake is conventionally dried, whereupon it is in merchantable form. The resulting filtrate is or may be discarded.

A part of the effluent from the thickeners is passed-by means of valved conduit 21ato the reaction vessel. The remainder of said efiiuent is passed-by means of valved conduit 2lbto the agitator equipped boiler section 22 of a recycle still wherein it is maintained at an elevated temperature of about 165 C. by conventional indirect heat exchange means, and is reacted with concentrated H2504 (admitted through conduit 40), to decompose the contents of metal salts of hydrofluosilicic acids to yield the free acid and sulphates of said metals. The overhead product passes into the upper-reliuxing-section 23 of the recycle still, in which latter section the vapor is contacted, in the packed column part 24 of section 23, with cooling liquid admitted through coolant line 25. Steam is discharged at 26, whilst a hydrouoric acid-containing solution of hydroiluosilicic acid accumulates in the base 27 of this section. Said concentrate is withdrawn by pump 28 and line 29, and is delivered partly to valved hydrofluosilicic acid solution make-up line 4 for use in reaction vessel l-and partly to a valved line 30 for delivery to a neutralizing vessel 31 equipped with agitating means 32. In vessel 31 the hydro- -uoric acid content of the solution is converted to hydrouosilicic acid by reaction with silica supplied thereto as at 33. The reaction mixture from vessel 31 passes by way of discharge conduit 34 onto a filter 35 where the excess silica is filtered out, as at 36, yielding a saleable, relatively concentrated, aqueous solution of hydrofiuosilicic acid which can be passed to storage through line 37.

In the exploitation of this process it frequently will transpire that the values in the bottom sludge 41 in the bottom section 22 of the recycle still warrant the slight expense of their recovery. In such event, the bottom sludgecomprising a relatively concentrated sulphuric acid and metal sulphates, e.g. sulfates of manganese, iron and aluminum-is diverted through pipe 42, onto a filter 43 thereby recovering (a) a concentrated sulphuric acid recycle which is returned by conduit 44 to the recycle still and (b) a filter cake composed of the aforesaid metal sulfates in crystalline form. As has been noted in this specification, the metal sulphates can-if the same is so desired-be caused by known procedures to yield up their metal values.

Reverting to the upgrading aspect of the invention, I now describe my preferred specific procedure:

In carrying out the solubilizing (i.e., leaching step on raw ore), the leach solution (i.e., the liquid phase of the dissolving zone) should have an H2SiF6 content of 10-15% by wt., and the free HF content (i.e., the recycled HF plus the make-up HF) per unit of raw ore should be about 10% by wt., more or less; and the solids in the resulting reaction mixture slurry should be from about 25 to about 30% by Wt. The agitated reaction mixture should pass through the dissolving zone in from about 0.5 to about 3.0 hours time. The optimum temperature for the solubilizing step appears to be in the range l00 C.

Raw ore at minus 100 mesh gm-- 50 30% HZSFS rnl 75 50% HF ml-- l0 and H2O I1'11 are slurried together and the slurry is heated to and maintained at about -100" C. for 30-50 minutes; the slurry then is filtered, and the separated phase is washed with water and dried.

The above procedure was used in processing the -following specific examples, demonstrating the chemistry of the upgrading process.

EXAMPLE I.AMPA ORE (BRAZIL) Raw Ore,

Processed Ore, Percent Percent (a) Coarse Fraction:

EXAMPLE IV.IMMINI (MOROCCAN) ORE EXAMPLE V.-URUCUM ORE (COARSE) I have found it advisable, in the above-described upgrading operation, to use about 2.0 pounds of wash water for each 1.0 pound of ore product. When (as is highly desirable) the upgrading is integrated into a cyclic process, about 0.2-0.4 pound of this 2.0 pounds of H2O will depart from the system in the form of a by-prod-uct 30% solution of HZSFG, and somewhat less than this amount Will depart in the sulfate sludge. Consequently, about 1.5 pounds of H2O must be volatilized, for each 1.0 pound of upgraded ore produced, in the distilling, or fluorinerecovering, step of the completed cycle.

The upgrading realizable by the observance of the principles of the present invention is, in almost all cases, very surprisingly substantial in extent and of Igreat technical advantage. This will be understood from a consideration of the extent of beneciation which I have realized -by carrying out the process of this invention-on the ores mentioned in the above specic examples.

The upgraded Mn02 ore product of this process has been improved in a number of significant and important respects; the Mn+4 content has been increased; the inactive gangue-including ironcontent has been minimized; the dioxide has been activated (resulting, in, many cases, in producing a true battery grade oxide from a relatively poor ore unusable in a battery): and the oxidation potential of the Mn02 has been improved. This elevation of a non-battery grade to a battery grade ore by the carrying out of the present process is particularly striking in the processing of an ore of the gamma. or rho crystalline type.

I claim:

1. Process of upgrading a manganese ore wherein a substantial part of the content of manganese-containing compounds consists of manganese dioxide, said ore containing a gangue constituent of the group consisting of compounds of Si, Al, Fe, P, Pb, Zn, Cu, Ca and Mg, which comprises treating the ore in particulate form With an aqueous solution of a dissolving agent of the group consisting of HF, H2SiF6 and mixtures of HF and H2S1'F5 whereby to leach out such gangue constituents land separating the resulting aqueous phase from the solid phase.

2. Process of upgrading a manganese ore wherein a su-bstantial part of the content of manganese-containing compounds consists of manganese dioxide, said ore containing a gangue constituent of the group consisting of com-pounds of Si, Al, Fe, P, Pb, Zn, Cu, Ca and Mg, which comprises treating the ore in particulate form with an aqueous solution of a dissolving agent of the group consisting of H-F, HgSiFf,l and mixtures of HF and HzSiFG whereby to produce an upgraded MnO2 product and an aqueous mother liquor containing solubilized gangue constituents and tluorine values, separating said product from said liquor and recovering the tluorine values from said mother liquor.

3. The process dened in claim 2 characterized in that the same is a cyclical process in which at least a substantial part of the recovered iluorine values is recycled as the aqueous solution of dissolving agent.

4. Cyclic process of upgrading a manganese ore wherein a substantial part of the content of manganese-containing compounds consists of manganese dioxide, said ore including a gangue constituent of the group consisting of compounds olf Si, Al, Fe, P, Pb, Zn, Cu, Ca and Mg, which comprises establishing a dissolving zone; feeding to the dissolving zone said ore in particulate form and an aqueous solution of HZSFG and HF; continuously removing from said zone a slurry of leached ore and mother liquor; separating leached ore from mother liquor and washing the leached ore; adding the Wash Water to the mother liquor; returning p-art of the mother liquor to the dissolving zone; reacting the remainder of the mother liquor with H2804, at an elevated temperature at least as high as C., thereby (a) forming sulfates of the soluble metal values off the mother liquor and (b) volatilizing the water and the fluorine values, the latter in the form of HF and SiF4; retiuxing the resulting vapors under conditions to yield (l) a vapor phase consisting essentially of water; and (2) a liquid phase consisting essentially of a 30% aqueous solution of H2SiF6 plus HF; returning a part of the resulting liquid phase to the dissolving zone; and removing the remainder of the liquid phase from the closed system.

5. Cyclic process of upgrading a manganese ore Wherein a substantial part of the content of manganese-containing compounds consists of manganese dioxide, said ore including a gangue constituent of the group consisting of compounds of Si, Al, Fe, P, Pb, Zn, Cu, Ca and Mg, which comprises establishing a dissolving zone; feeding to the dissolving zone said ore in particulate form and an aqueous solution of H2SiF6 and HF; continuously removing from said zone a slurry of leached ore and mother liquor; separating leached ore from the mother liquor and washing the leached ore; adding the wash water to the mother liquor; returning part of the mother liquor to the dissolving zone; reacting the remainder of the mother liquor with H2804, at an elevated temperature at least as high as 160 C., thereby (a) rforming sulfates of the soluble metal values of the mother liquor and (b) volatilizing the water and the uorine values, the latter in the form o-f HF and Sil-14; reiiuxing the resulting vapors under conditions to yield 1) a liquid phase consisting essentially of a l5-43% aqueous solution of HZSiFS plus HF and (2) a vapor phase consisting essentially of water; returning a part of the resulting liquid phase to the dissolving zone; `and treating the remainder of the liquid phase from the refluxing operation with silica in an amount at least equal to the free HF content of said liquid phase, whereby to produce HgSiFG product.

6. Cyclic process of upgrading a manganese ore wherein a substantial part of the content of manganese-containing compounds consists of manganese dioxide, said ore including a gangue constituent of the group consisting of compounds of Si, Al, Fe, P, Pb, Zn, Cu, Ca and Mg which comprises establishing a dissolving zone; feeding to the dissolving zone said ore in particulate form and an aqueous solution of H2SiF6 and HF; said dissolving agent containing from about 10 to about 15% by wt. of HzSiFs based on the solution and about 10% of total free HF (in recycled solution plus make-up addition) based on Weight of raw ore, and the solids in the resulting slurry being from about 25 to about 30% by weight', continuously removing from said zone a slurry of leached ore and mother liquor; separating leached ore from the mother liquor and Washing the leached ore; adding the Wash water to the mother liquor; returning part of the mother liquor to the dissolving Zone; reacting the remainder of the mother liquor with H2804, at an elevated temperature at least as high at 160 C., thereby (a) forming sulfates of the soluble metal values of the mother liquor and (b) volatilizing the Water and the uorine values, the latter in the form of HF and SiF4; reuxing the resulting vapors under conditions to yield (l) a liquid phase consisting essentially of a l543% aqueous solution of H2SiF6 plus HF and (2) a vapor .phase consisting essentially of water; returning a part of the resulting liquid phase to the dissolving zone; and treating the remainder of the liquid phase from the refluxing operation with silica in an amount at least equal to the free HF content of said liquid phase, whereby to produce HZSiF product.

References Cited UNITED STATES PATENTS DAVID L. RECK, Primary Examiner. N. F. MARKVA, Assistant Examiner. 

1. PROCESS OF UPGRADING A MANGANESE ORE WHEREIN A SUBSTANTIAL PART OF THE CONTENT OF MANGANESE-CONTAINING COMPOUNDS CONSISTS OF MANGANESE DIOXIDE, SAID OR CONTAINING A GANGUE CONSTITUENT OF THE GROUP CONSISTING OF COMPOUNDS OF SI, AL, FE, P, PB, ZN, CU, CA AND MG, WHICH COMPRISES TREATING THE ORE IN PARTICULATE FORM WITH AN AQUEOUS SOLUTION OF A DISSOLVING AGENT OF THE GROUP CONSISTING OF HF, H2SIF6 AND MIXTURES OF HF AND H2SIF6 WHEREBY TO LEACH OUT SUCH GANGUE CONSTITUENTS AND SEPARATING THE RESULTING AQUEOUS PHASE FROM THE SOLID PHASE. 